Fossil-fire steam power stations serve primarily for covering the base load in the public electricity supply, that is to say the load of the public electricity network as a result of a power demand which typically does not fall below a specific level on a daily average. Reference is especially made to oil-fired or coal-fired steam power stations as such. For covering further required quantities of electricity, medium power stations or peak power stations are used in the case of corresponding demand.
The steam power stations which are fired with oil or coal are operated as base load power stations on account of the high fixed operating costs and the relatively low fuel costs. During operation, they are operated preferably in the upper load range round the clock, in a manner which is typical to base load. By the same token, depending on technical design, they can also be suitable as medium-load power stations on account of their comparatively advantageous startup speeds or fast controllability.
Since such steam power stations are preferably used in continuous operation, they are especially suitable during times of low electricity demands for feeding into temporary storage systems from which the electric energy can be quickly made available again in the event of renewed electricity demand.
Such temporary storage systems are, for example, industrial electrical batteries which are capable of storing power station capacities of electric energy in electric form. In connection with the provision of electric energy in the public electricity networks, the high-temperature battery technology in particular has proved to be suitable in this case.
Such batteries which are suitable for temporarily storing power station capacities of electric power in order to be able to deliver these capacities in sufficient quantity to the public electricity network again when required, are to be understood as high-temperature batteries in this case. Also, the operating temperatures of these high-temperature batteries is to be at least 100° C., preferably more than 250° C. and most especially preferably more than 500° C. High-temperature batteries are preferably solid-electrolyte batteries with an operating temperature which is referred to above.
Consequently, the sodium-sulfur cell (Na-S-accumulator), for example, is therefore suitable for temporarily storing even larger quantities of electric power. These quantities can be delivered again at very short notice during peak load times or for network stabilization in the public electricity network. A further high-temperature battery technology, which is suitable for the supply at peak load times, is a metal-air battery developed by the applicant, as is described in DE 10 2009 057 720 A1, for example. The contents of this document may be expressly incorporated herewith into this present application by reference. This metal-air battery is distinguished by the presence of an oxidizable material, preferably a metallic material, such as iron, which is oxidized by steam during the discharging of the battery. The power output of the battery is based, moreover, on a cathode-side process gas feed, which typically is supplied with air as process gas. The oxygen present in the air is reduced in this case during a discharging state on the cathode and by means of a gastight solid electrolyte, which separates cathode and anode, is transported into the anode region. Oxidation of the reduced oxygen is carried out there, wherein the released electric charge can be tapped off via contacts as electric power. So that the solid electrolyte can ensure its ionic conductivity in an operating state, the functioning capability of the metal-air battery requires a minimum temperature which cannot be fallen short of for an economical operation.
Common to all high-temperature batteries is that they require supplying with thermal energy for an economical operation. In order to provide this, electric heating systems are typically integrated into the respective batteries as heat sources in order to be able to bring these to operating temperature or to hold these at operating temperature. This, however, often proves to be economically unprofitable in an overall consideration of the electric capacities to be used since the supply with electric energy is distinguished by undesirable power losses during the production, provision and intermediate storage.
Added to these power losses, moreover, are also thermal losses since the operating temperatures of approximately more than 250° C. or of more than 500° C. mean not only a high supply cost for providing the thermal energy which is produced from electric energy but also require a high insulation cost in order to minimize the thermal losses as far as possible.